import cv2
import numpy as np
img=cv2.imread('yihun.jpg',cv2.IMREAD_GRAYSCALE)
rows,cols=img.shape[:2]
circle=np.zeros((rows,cols),dtype='uint8')
cv2.circle(circle,(int(rows/2),int(cols/2)),150,255,-1)
result =cv2.bitwise_xor(img ,circle)
cv2.imshow('c1',img)
cv2.imshow('c2',result)
cv2.imshow('c3',circle)
cv2.waitKey()
cv2.destroyAllWindows()